1. Field of the Invention
The present invention relates to the field of techniques for avoiding or reducing the adverse influence of a product formed on a substrate by a vacuum process and exposed to the atmosphere on the components of an atmospheric carrying chamber when the substrate processed by the vacuum process is carried to the atmospheric carrying chamber.
2. Description of the Related Art
A substrate, such as a semiconductor wafer (hereinafter, referred to simply as “wafer”), is subjected to a vacuum process, such as a plasma processing process, for example, an etching process, to fabricate a semiconductor devices. A vacuum processing system called a multichamber system is used to carry out such a process at a high throughput.
FIG. 11 shows a known vacuum processing system provided with a vacuum processing chamber and an atmospheric carrying chamber by way of example. Referring to FIG. 11, this known vacuum processing system includes front opening unified pod (abbreviated to “FOUP”)) tables 10 for supporting thereon a FOUP, namely, a carrying container containing a plurality of wafers, for example twenty-five wafers, a transfer module (TM) 11 provided with a carrying arm for carrying a wafer and maintaining a vacuum atmosphere, four process modules (PM) 12a, 12b, 12c and 12d for processing a wafer by predetermined processes in a vacuum atmosphere, a loader module (LM) 14 provided with a carrying mechanism including a carrying arm for carrying a wafer and maintained in an atmospheric atmosphere, two load-lock modules (LLM) 15a and 15b disposed between the loader module 14 and the transfer module 11, and capable of being selectively set in either of a vacuum atmosphere and a normal-pressure atmosphere, and an orienter (ORT), not shown, disposed so as to adjoin the loader module 14 for the prealignment of a wafer. In FIG. 11, indicated at G11 to G14 are gate valves.
A wafer carrying route in the vacuum processing system will be briefly described. A wafer to be processed taken out from a FOUP supported on the FOUP table 10 is carried along a carrying route passing the LM, the ORT, the LLM, the TM and the PM in that order. The wafer is processed by, for example, an etching process in the process module 12a (12b, 12c, 12d) in an atmosphere of a process gas. The wafer thus processed is carried along a carrying route passing the TM, the LLM and LM in that order and is returned to the FOUP supported on the FOUP table 10.
In some cases, gases generated by the reaction of byproducts produced on the wafer during processing the wafer with moisture contained in the atmosphere condense in liquids on wafers not yet processed during the operation for returning the processed wafer to the FOUP placed on the FOUP table 10. The liquids thus produced can cause defects in devices. A purge storage 13 is connected to the loader module 14 as indicated by broken lines in FIG. 11. The processed wafer is held temporarily in the purge storage 13 to prevent such cross-contamination.
However, the following problem arises when the processed wafer is carried from the load-lock module 15a (or 15b) through the loader module 14 to the purge storage 13. For example, a process gas, such as HBr gas or Cl2 gas, is ionized in the process module 12a (12b, 12c, 12d) to generate a plasma for etching a polysilicon film formed on a wafer by an etching process. During the etching process, a byproduct, such as silicon bromide or silicon chloride, is produced on the wafer. When the wafer carrying the byproduct is carried into the loader module 14 in the atmospheric atmosphere, the silicon bromide or the silicon chloride react with moisture contained in the atmosphere and, consequently, a corrosive gas, such as hydrogen bromide gas or hydrogen chloride gas, is produced. The corrosive gas diffuses, and the corrosive gas reacts with a small amount of ammonia contained in the atmosphere to produce ammonium bromide particles or ammonium chloride particles. The particles diffuse in the loader module 14. Consequently, metal parts of the loader module 14, such as walls defining a carrying chamber, and components of the carrying mechanism, are corroded. It is possible that the corroded parts are abraded during mechanical motions and cause metal contamination. It is also possible that the particles adhere to the internal parts of the loader module 14 and cause particle contamination.
It is mentioned in JP-A 2005-50852 that entrained contaminants adhered to a sample in a plasma processing system react with moisture contained in the atmosphere to produce new contaminants or to create a corrosive environment that corrodes structural members. A carrying procedure intended to prevent such troubles mentioned in JP-A 2005-50852 carries a sample into or carries out a sample from an evacuated load-lock chamber in a state where a gas is supplied through a gas inlet port into the load-lock chamber, a gate valve on the side of the atmosphere is opened, the gas is supplied continuously into the load-lock chamber, a gas is supplied through a gas inlet port formed in a cover, and an atmosphere in the load-lock chamber is discharged through an exhaust port formed in the cover. However, even if currents is generated in the load-lock chamber to remove contaminants adhering to a wafer, the contaminants cannot be removed by the currents in a short time because the wafer can be held in the load-lock chamber only a short time in consideration of throughput.